JP7629406B2 - Resin container manufacturing method and resin container manufacturing device - Google Patents

Description

The present disclosure relates to a method for manufacturing a resin container and an apparatus for manufacturing a resin container.

The hot parison blow molding method utilizes the heat retained during injection molding of the preform to produce a wider variety of containers with a more aesthetically pleasing appearance than the cold parison blow molding method. Hot parison blow molding machines come in two types: models with a temperature control section between the injection molding section and the blow molding section (four-station type) and models without (two-station type and three-station type). The presence of a temperature control section generally makes it easier to adjust the temperature conditions of the preform before blowing to one suitable for shaping the final container.

Furthermore, various methods and devices have been developed for the purpose of shortening the molding cycle in hot parison blow molding machines. For example, Patent Document 1 and Patent Document 2 shorten the time required for opening and closing the injection molding die and for raising and lowering the stretching device, Patent Document 3 changes the control method for the injection device, and Patent Document 4 employs a preform shape that allows for early demolding and an injection molding die for that preform, thereby shortening the molding cycle.

Japanese Patent Application Publication No. 2005-007797 International Publication No. 2016-148189 International Publication No. 2017-002150 International Publication No. 2017-098673

In addition to the techniques described in Patent Documents 1 to 4 above, techniques have been developed to shorten the molding cycle by shortening the cooling time of the preform in the injection molding process and then performing post-cooling in a temperature adjustment process. However, the inventors have discovered a technical problem in that containers manufactured by blow molding using this method are prone to residual material defects in the shoulders due to insufficient stretching during blow molding, and the container's wall thickness distribution tends to be poorly formed, resulting in a deterioration in aesthetic appearance and physical properties.

Therefore, the present disclosure aims to provide a manufacturing method and manufacturing apparatus for resin containers that shortens the molding cycle time by post-cooling in a temperature adjustment process while reducing the risk of residual material remaining on the shoulder of the container.

In order to achieve the above object, the method for producing a resin container according to the present disclosure includes:
an injection molding step of injection molding a resin preform having a neck portion and a body portion;
a temperature control step of cooling and controlling the temperature of the injection molded preform;
A blow molding process for producing a resin container by blow molding the temperature-controlled preform,
In the injection molding step,
a step portion is formed between the neck portion and the body portion of the preform, the step portion being thicker than the engagement groove of the neck portion, and the outer diameter of the step portion is formed to be larger than the outer diameter of the engagement groove of the neck portion,
In the blow molding step,
The preform is blow molded such that at least a portion of the step portion remains between a neck portion and a shoulder portion of a container blow molded based on the preform.

According to the above method, in the blow molding process, a preform having a step portion with high retained heat is stretch-blowed so that at least a part of the step portion remains between the neck portion and shoulder portion of the container, thereby enabling good stretch-blowing from the neck portion to the shoulder portion of the container.
In this manner, according to the above-described method, it is possible to provide a manufacturing method in which the molding cycle time is shortened by post-cooling in the temperature adjustment step, while preventing defects such as residual material on the shoulder portion of the container.

In addition, the manufacturing apparatus for a resin container according to the present disclosure includes:
an injection molding unit that injection molds a resin preform having a neck portion and a body portion;
A temperature control unit that cools and controls the temperature of the injection molded preform;
a blow molding section for blow molding the temperature-controlled preform to manufacture a resin container,
the injection molding part forms a step part between the neck part and the body part of the preform, the step part being thicker than the neck part, and the outer diameter of the step part is larger than at least the outer diameter of the engagement groove of the neck part of the preform;
The temperature adjustment unit simultaneously cools the body portion of the preform from the inside and the outside of the body portion,
The blow molding section blows the preform so that at least a portion of the step portion remains between a neck portion and a shoulder portion of a container blow molded based on the preform.

According to the above configuration, in the blow molding section, a preform having a step portion with high retained heat is stretch-blowed so that at least a part of the step portion remains between the neck portion and shoulder portion of the container, thereby enabling good stretch-blowing from the neck portion to the shoulder portion of the container.
In this manner, according to the above-described configuration, it is possible to provide a manufacturing apparatus which reduces the molding cycle time by post-cooling in the temperature adjustment section, while preventing defects such as residual material on the shoulder of the container.

According to the present disclosure, a manufacturing method and manufacturing apparatus for resin containers can be provided that shortens the molding cycle time by post-cooling in a temperature adjustment process while reducing the risk of residual material remaining in the shoulder area of the container.

1 is a schematic diagram showing a resin container manufacturing apparatus according to an embodiment of the present disclosure. FIG. 2 is a diagram illustrating an injection molding die that constitutes an injection molding section. FIG. 2 is a diagram illustrating a temperature control mold that constitutes a temperature control unit. FIG. 2 is a diagram illustrating a blow molding die that constitutes a blow molding section. 11 is a diagram showing a step portion remaining in a blow-molded resin container. FIG. 1 is a flowchart illustrating a method for manufacturing a resin container. 13A and 13B are diagrams illustrating a support ring formed in a neck portion. FIG. 13 is a diagram showing a modified example of the injection molding die. FIG. 13 is a diagram showing a modified example of a preform formed by injection molding.

Hereinafter, an embodiment of the present disclosure will be described with reference to the drawings. Note that the dimensions of each component shown in the drawings may differ from the actual dimensions of each component for the sake of convenience.

A resin container manufacturing apparatus 10 according to an embodiment will be described with reference to FIGS. 1 to 5. FIG.
Fig. 1 is a schematic diagram showing a resin container manufacturing apparatus 10. As shown in Fig. 1, the resin container manufacturing apparatus 10 includes an injection molding section 11 for injection molding a preform for a resin container, and a temperature control section 12 for controlling the temperature of the formed preform. An injection device 15 for supplying a resin material, which is a raw material for the resin container, is connected to the injection molding section 11. The resin container manufacturing apparatus 10 also includes a blow molding section 13 for blowing the temperature-controlled preform to manufacture a resin container, and a removal section 14 for removing the manufactured resin container.

The preforms and resin containers are transported by the transport means 16 in the order of the injection molding section 11, the temperature control section 12, the blow molding section 13, and the removal section 14 in the resin container manufacturing apparatus 10. The injection molding section 11, the temperature control section 12, the blow molding section 13, and the removal section 14 are located at positions rotated by a predetermined angle (90 degrees in this embodiment) around the transport means 16. The transport means 16 is composed of, for example, a rotating plate, and transports the preforms and resin containers to each section as the rotating plate rotates. As shown in Figures 2 to 4, the preforms and resin containers are transported to each section as the rotating plate rotates with the neck section 21 supported by the neck mold 102 attached to the rotating plate. The resin container manufacturing apparatus 10 is a hot parison type manufacturing apparatus in which the temperature control section 12 is provided between the injection molding section 11 and the blow molding section 13, and continuously manufactures preforms and resin containers.

2 is a cross-sectional view of the injection molding die 100 constituting the injection molding section 11. As shown in F2A of FIG. 2, the injection molding die 100 includes a neck die 102, an injection core die 104, and an injection cavity die 106. The injection molding die 100 is configured to form a preform 20 by pouring (filling with molten resin) a synthetic resin material such as a polyester resin (e.g., PET: polyethylene terephthalate) into a cavity formed by clamping these dies.

The preform 20 has a neck portion 21, a step portion 22 connected to the neck portion 21, a body portion 23 connected to the step portion 22, and a bottom portion 24 connected to the body portion 23. The step portion 22 is an intermediate connection portion provided between the neck portion 21 and the body portion 23, and is a portion that protrudes in the outer diameter direction from the lower end T of the neck portion 21. As shown in F2B (partially enlarged view) of FIG. 2, the thickness T2 of the step portion 22 is formed to be thicker than at least the thickness T1 of the engagement groove 21a of the neck portion 21. The thickness T2 of the step portion 22 may be the same as the thickness of the engagement protrusion 21b, or may be thicker or thinner than the thickness of the engagement protrusion 21b. The outer diameter of the step portion 22 is formed to be larger than at least the outer diameter of the engagement groove 21a of the neck portion 21. The outer diameter of the step portion 22 may be the same as the outer diameter of the engagement protrusion 21b, or may be larger or smaller. 2F2C (partially enlarged view), a first corner is provided between the outer wall surface of the lower part of the neck portion 21 (the lower part of the lowest engaging protrusion 21b) and the upper surface of the step portion 22, and the angle K1 is set to, for example, 90° to 110°. Also, a second corner is provided between the upper surface and the side surface of the step portion 22, and the angle K2 is set to, for example, 80° to 100°.

The step portion 22 of the preform 20 is composed of an upper step portion 22a defined by a part of the lower cavity surface of the neck mold 102, and a lower step portion 22b defined by a part of the upper cavity surface of the injection cavity mold 106. The upper step portion 22a is formed between the neck portion 21 and the lower step portion 22b. The lower step portion 22b is formed between the upper step portion 22a and the body portion 23. As shown in F2B of FIG. 2, in this example, the vertical length of the upper step portion 22a and the vertical length of the lower step portion 22b are approximately the same. The boundary between the upper step portion 22a and the lower step portion 22b is located at a position corresponding to the parting surface between the bottom surface of the neck mold 102 and the top surface of the injection cavity mold 106, so that a trace corresponding to the parting line may be formed at the boundary. The upper step portion 22a may be set to a region 1.5 mm to 2.0 mm above the step portion 22 with the lower end T of the neck portion 21 as the base end, and the lower step portion 22b may be set to a 1.5 mm region adjacent thereto.

In this example, the outer wall surface of the step portion 22 and the outer wall surface of the body portion 23 are connected, and are formed, for example, to be substantially flush or to have a gently tapered portion (e.g., tapered shape) in between. The body portion 23 is formed so that its inner wall surface gradually slopes toward the center of the preform 20 as it approaches the bottom portion 24 of the preform 20, and the inner diameter of the body portion 23 gradually becomes smaller as it approaches the bottom portion 24 of the preform 20.

The neck mold 102 has an outer neck defining portion 111, which is a cavity surface that defines the outer shape of the neck portion 21 of the preform 20, and an outer step defining portion 112, which is a cavity surface that defines the outer shape of the upper step portion 22a of the step portion 22 of the preform 20. The inner diameter of the outer step defining portion 112 is formed to be at least larger than the inner diameter of the portion of the outer neck defining portion 111 that defines the engagement groove 21a of the neck portion 21. The inner diameter of the outer step defining portion 112 may be the same as the inner diameter of the portion of the outer neck defining portion 111 that defines the engagement protrusion 21b of the neck portion 21, or may be larger or smaller than the inner diameter of the portion that defines the engagement protrusion 21b.

The injection core mold 104 has an inner neck defining portion 121 that defines the inner shape of the neck portion 21 of the preform 20, an inner step defining portion 122 that defines the inner shape of the step portion 22 of the preform 20, an inner body defining portion 123 that defines the inner shape of the body portion 23 of the preform 20, and an inner bottom defining portion 124 that defines the inner shape of the bottom portion 24 of the preform 20. The inner step defining portion 122 is continuous with the inner neck defining portion 121, the inner body defining portion 123 is continuous with the inner step defining portion 122, and the inner bottom defining portion 124 is continuous with the inner body defining portion 123. A portion of the injection core mold 104 including the inner neck defining portion 121, the inner step defining portion 122, the inner body defining portion 123, and the inner bottom defining portion 124 is tapered. The injection core mold 104 is configured to be able to rise and fall in the vertical direction Y1 in FIG. The injection core mold 104 shown in FIG. 2 is in the middle of ascending upward after the formation of the preform 20 has been completed.

The injection cavity mold 106 has an outer body defining portion 131 that defines the outer shape of the body portion 23 of the preform 20, an outer bottom defining portion 132 that defines the outer shape of the bottom portion 24 of the preform 20, an opening 133 located on the opposite side of the outer bottom defining portion 132 across the outer body defining portion 131, and an outer step defining portion 134 that is a cavity surface that defines the outer shape of the lower step portion 22b of the step portion 22. A hot runner 108 is connected to the lower part of the injection cavity mold 106. The hot runner 108 is connected to the injection device 15. Molten resin such as PET is filled from the injection device 15 through the hot runner 108.

3 is a cross-sectional view of the temperature control mold 200 constituting the temperature control section 12. As shown in Fig. 3, the temperature control mold 200 has a neck mold 102, a temperature control core mold (temperature control blow core mold) 202, an air introduction rod 203, and a temperature control cavity mold 204. The neck mold 102 is a common neck mold that moves to the position of the temperature control mold 200 while holding the preform 20 formed in the injection molding section 11.

The temperature-controlling core mold 202 is configured to be able to rise and fall in the vertical direction Y2 in Fig. 3. As shown in Fig. 3, when the neck mold 102 and the temperature-controlling cavity mold 204 are clamped together and the temperature-controlling core mold 202 is lowered and inserted into the neck mold 102, the temperature-controlling core mold 202 is configured to fit or come into contact with the neck portion 21 of the preform 20. This makes it possible to prevent air inside the preform 20 from leaking from the neck portion 21 to the outside of the temperature-controlling core mold 202.

The air introduction rod 203 is configured to be movable up and down in the vertical direction Y2 in Fig. 3 inside the temperature control core mold 202. The tip of the air introduction rod 203 is provided with a first internal circulation port 221 that can blow out or exhaust air (air supply or exhaust: supply and exhaust).

The gap between the temperature-controlling core mold 202 and the air introduction rod 203 is a circulation path for supplying and discharging air to and from the preform 20. The gap formed between the tip of the temperature-controlling core mold 202 and the air introduction rod 203 constitutes a first outer circulation port 222 that can blow or suck air. The first inner circulation port 221 and the first outer circulation port 222 can be an air supply port and an exhaust port, respectively.

The temperature-controlled cavity mold 204 accommodates the preform 20 formed in the injection molding section 11. A cooling medium circulation path 205 is provided inside the temperature-controlled cavity mold 204. A cooling medium such as water flows through the cooling medium circulation path 205. The temperature-controlled mold 200 accommodates the preform 20 formed in the injection molding section 11 in the temperature-controlled cavity mold 204, and is configured to cool and adjust the temperature of the preform 20 to a temperature suitable for blow molding. The temperature of the cooling medium flowing through the cooling medium circulation path 205 is set to, for example, about 10°C to about 65°C.

The temperature-controlled mold 200 adjusts the temperature by simultaneously cooling the neck portion 21, step portion 22, body portion 23, and bottom portion 24 of the injection-molded preform 20 from the inside and outside using air blown in from an air introduction rod 203 and direct cooling by a temperature-controlled cavity mold 204.
The heater 206 may be provided on the upper part of the temperature-controlled cavity mold 204 facing the step portion 22. This heater 206 is not intended to heat the body portion 23.

Figure 4 is a cross-sectional view of the blow molding die 300 that constitutes the blow molding section 13. F4A in Figure 4 shows the state in which the preform 20 is contained in the blow molding die 300. F4B in Figure 4 shows the state in which the preform 20 has been inflated to the shape of the resin container 30.

As shown in F4A and F4B of FIG. 4, the blow molding die 300 includes a neck die 102, a blow core die 302, a stretch rod 304, a blow cavity die 306, and a bottom die 308. The neck die 102 is a common neck die that moves to the position of the blow molding die 300 while holding the preform 20 whose temperature has been adjusted by the temperature adjustment unit 12. The blow molding die 300 stretches the preform 20 whose temperature has been adjusted by the temperature adjustment unit 12 with the stretch rod 304, while introducing air from the blow core die 302 to inflate the preform 20 into a shape defined by the blow cavity die 306 and the bottom die 308, thereby forming a resin container 30.

The blow cavity mold 306 and the bottom mold 308 are clamped together to define the outer shape of the side and bottom surfaces of the resin container 30. The bottom mold 308 is positioned at the lower center of the molding space of the blow cavity mold 306.

The stretch rod 304 is configured to be movable up and down in the vertical direction Y3 in FIG. 4 inside the blow core mold 302. The tip of the stretch rod 304 is provided with a contact portion 311 that contacts the inner bottom surface of the preform 20 to prevent misalignment during stretching. The outer peripheral surface of the stretch rod 304 is formed with a second inward flow port 312 through which air can be ejected.

4 in which the neck mold 102, the blow cavity mold 306, and the bottom mold 308 are clamped together, the blow core mold 302 is configured to fit or abut against the neck portion 21 of the preform 20 when inserted into the neck mold 102. This prevents air inside the preform 20 from leaking from the neck portion 21 to the outside of the blow core mold 302.

The gap between the stretch rod 304 and the blow core mold 302 is a circulation path for supplying and discharging air to and from the preform 20. The gap formed between the tip of the blow core mold 302 and the stretch rod 304 constitutes a second outer circulation port 313 capable of sucking in air. The stretch rod 304 is configured so that air can be sprayed from the second inner circulation port 312 into the inside of the preform 20. The second inner circulation port 312 is an air supply port, and the second outer circulation port 313 is an exhaust port.

Figure 5 is a cross-sectional view of a blow-molded resin container 30. As shown in Figure 5, the resin container 30 has an upper step portion 22a between the neck portion 21 and the shoulder portion 36. The upper step portion 22a is a part of the step portion 22 formed in the preform 20 during injection molding of the preform 20. The blow molding section 13 blow molds the preform 20 so that at least a part of the step portion 22 formed during injection molding of the preform 20 remains between the neck portion 21 and the shoulder portion 36 of the resin container 30. An example of an event in which at least a part of the step 22 remains between the neck portion 21 and the shoulder portion 36 of the resin container 30 includes, for example, a case in which a trace (line) of the step portion 22 remains on the shoulder portion 36 of the resin container 30.

The removal section 14 is configured to allow the resin container 30 to be removed by releasing the neck portion 21 of the resin container 30 from the neck mold 102.

Next, a method for manufacturing a resin container 30 according to an embodiment will be described with reference to Figure 6 and Figures 2 to 5. Figure 6 is a flow chart for explaining a method for manufacturing a resin container 30. As shown in Figure 6, the method for manufacturing a resin container 30 includes at least an injection molding process S1 for injection molding a preform 20, a temperature adjustment process S2 for adjusting the temperature of the preform 20, a blow molding process S3 for blow molding the preform 20 to form a resin container 30, and a removal process S4.

First, the injection molding process S1 will be described. In the injection molding process S1, the injection molding die 100 consisting of the neck die 102, the injection core die 104, and the injection cavity die 106 is clamped. Next, the cavity of the clamped injection molding die 100 is filled with resin material from the injection device 15 via the hot runner 108.

In the injection molding process S1, a step portion 22 is molded between the neck portion 21 and the body portion 23 of the preform 20. As shown in FIG. 2F2B, the step portion 22 is molded so that its thickness T2 is at least thicker than the thickness T1 of the engagement groove 21a of the neck portion 21. The step portion 22 is molded so that its outer diameter is at least larger than the outer diameter of the engagement groove 21a of the neck portion 21. The step portion 22 is molded so that its outer wall surface is approximately flush with the outer wall surface of the body portion 23 or has a reduced diameter portion (e.g., tapered shape) between the outer wall surface of the body portion 23. The inner wall surface of the body portion 23 gradually inclines toward the center of the preform 20 as it approaches the bottom portion 24 of the preform 20, and the inner diameter of the body portion 23 gradually becomes thinner. The body portion 23 may be molded so that its thickness gradually increases as it approaches the bottom portion 24.

After the resin material has been filled into the cavity of the clamped injection mold 100, the clamped state is maintained for a predetermined time, and then the mold is released to form the preform 20. At this time, in order to cool the resin material filled in the cavity, a cooling medium is passed through the circulation paths provided in the injection core mold 104 and the injection cavity mold 106. The cooling medium is set to a temperature within the range of, for example, about 5°C to about 20°C.

The molded preform 20 is raised together with the injection core mold 104 and the neck mold 102 to release the preform 20 from the injection cavity mold 106. Next, the injection core mold 104 is further raised to release the injection core mold 104 from the preform 20. Then, the preform 20 held by the neck mold 102 is rotated together with the neck mold 102 by the conveying means 16 and moved to the temperature adjustment section 12 (temperature adjustment process).

Next, the temperature control process S2 will be described. In the temperature control process S2, first, the preform 20 moved to the temperature control section 12 is accommodated in the temperature control cavity mold 204 by lowering the neck mold 102. Next, the temperature control core mold 202 is lowered to abut the inner surface of the preform 20. Furthermore, the air introduction rod 203 is lowered and inserted into the inside of the preform 20. Then, with the first inner circulation port 221 closed, air is sent from the first outer circulation port 222 to the inside of the preform 20, and a preliminary blow is performed to make the preform 20 adhere to the inner wall of the temperature control cavity mold 204. Next, the first inner circulation port 221 is opened, and a cooling blow is performed in which air is introduced from the first inner circulation port 221 while air is discharged to the outside of the preform 20 through the first outer circulation port 222 (FIG. 3). In this way, it is preferable to set the air flow direction in the preliminary blow and the cooling blow in the opposite direction. The preliminary blow may not necessarily be performed. The cooling blow may be performed by a method in which air is introduced from the first outer circulation port 222 while the air is discharged to the outside of the preform 20 through the first inner circulation port 221.

At this time, air continues to be blown out from the first internal flow port 221, so that the body 23 of the preform 20 is cooled from the inside (the inner surface side) by the convection of the air flowing inside. At the same time, the body 23 is also cooled from the outside (the outer surface side) by bringing the preform 20 into contact with the temperature-controlled cavity mold 204. In this way, the temperature of the preform 20 is adjusted to a temperature suitable for blow molding.

In addition, if the heater 206 is provided on the upper part of the temperature-controlled cavity mold 204, it is possible to adjust the temperature (heat amount adjustment) by heating the step portion 22, so that the temperature of the step portion 22 can be controlled more precisely.

After the temperature is adjusted, the temperature-controlled core mold 202 and the air introduction rod 203 are raised to release the preform 20 from the temperature-controlled core mold 202. Next, the neck mold 102 holding the preform 20 is raised to release the preform 20 from the temperature-controlled cavity mold 204. Then, the preform 20 held by the neck mold 102 is rotated together with the neck mold 102 by the conveying means 16 and moved to the blow molding section 13 (blow molding process).

Next, the blow molding process S3 will be described. In the blow molding process S3, as shown in F4A of Fig. 4, the preform 20 is placed in the blow cavity mold 306. Next, as shown in F4B of Fig. 4, the preform 20 is stretched by the stretch rod 304 while blow air is introduced from the blow core mold 302 to inflate the preform 20 to the shape of the blow cavity mold 306, thereby forming the resin container 30.

In the blow molding process S3, as shown in Fig. 5, the preform 20 is blow molded into the resin container 30 so that at least a portion of the step portion 22 (including the upper step portion 22a) formed during the injection molding of the preform 20 remains between the neck portion 21 and the shoulder portion 36 of the resin container 30. After blow molding, the resin container 30 is released from the blow molding die 300 and moved to the removal section 14.

By the way, a hot parison blow molding method has been devised that enables high cycle by shortening the cooling time of the injection molding process, releasing the preform from the injection mold at a high temperature, and supplementing the insufficient cooling of the preform by post-cooling (additional cooling) in the temperature control process. This method can suppress whitening (crystallization) caused by slow cooling of crystalline plastics such as PET, and makes it possible to manufacture high-quality containers at high speed. However, the preform molded by this method has a problem that the lower region of the neck (the boundary between the neck and the body) is easily cooled. The reason for this is that the diameter of the neck and the lower region of the neck are approximately the same, the thickness of the lower region is approximately the same as the thickness of the thin neck, the amount of heat (retained heat) of the lower region of the neck during injection molding is small, and further, the amount of heat of the lower region of the neck is taken away through the nearby mold. In addition, in this method, the preform is cooled in the temperature control process to maintain a high cycle, so it is difficult to reheat in the temperature control process, and there is a high risk that the lower region of the neck will cool further. When a container is formed by blow molding a preform in a state where the region below the neck is cooled, a residual wall defect (poor wall thickness distribution) occurs in the shoulder area, which corresponds to the region below the neck. The poor wall thickness distribution of the container reduces the aesthetic appearance and physical properties (strength and rigidity). Therefore, it is desired to develop a method and device that can suppress the residual wall defect that occurs in the shoulder area of the container in the high-cycle hot parison blow molding method.

In contrast, according to the method for manufacturing a resin container having the above-mentioned steps, the preform 20 is post-cooled in the temperature adjustment step S2, thereby shortening the cooling time in the injection molding step S1.

In addition, in the injection molding process S1, a step portion 22 that is thicker than at least the engagement groove 21a of the neck portion 21 is formed between the neck portion 21 and the body portion 23 of the preform 20. This step portion 22, which corresponds to the lower region of the neck portion described above, is thicker than at least the engagement groove 21a of the neck portion 21. In addition, the outer diameter of the step portion 22 is molded to be larger than the outer diameter of the engagement groove 21a of the neck portion 21 of the preform 20.

According to the above configuration, the upper step portion 22a of the step portion 22 that contacts the neck mold 102 has a low heat retention at low temperatures, but the lower step portion 22b that does not contact the neck mold 102 can retain a higher amount of heat than a preform of a conventional shape by increasing the thickness. Next, in the blow molding process S3, the preform 20 having the thick step portion 22 with high retained heat is stretch-blown so that at least a part of the step portion 22 (a part including at least a part of the upper step portion 22a) remains between the neck portion 21 and the shoulder portion 36 of the resin container 30. Therefore, the part including the thick lower step portion 22b with high retained heat can be stretch-blown well to the part from the neck portion 21 to the shoulder portion 36 of the resin container 30.

In addition, by molding the outer diameter of the step portion 22 to be larger than the outer diameter of the engagement groove 21a of the neck portion 21 of the preform 20, it is possible to secure space in the injection cavity 106 for forming the body portion 22 of the preform 20 to be thick without changing the shape of the injection core mold 104.

In addition, in order to manufacture a resin container with good appearance and physical properties using the above-mentioned high-cycle hot parison blow molding method, it is desirable to use a preform with a thick body and a short length, and to increase the stretch ratio during blow molding. However, the conventional design method for making the body of a preform thick was to make the outer wall surface of the neck and body approximately flush (to make the diameter approximately the same) and to bias the inner wall surface of the body toward the central axis of the preform. However, as a result, it becomes necessary to make the injection core mold thinner (to make the diameter smaller). Since a cooling medium circulation path is provided inside the injection core mold, it cannot be made thinner than a certain amount. In particular, the inner diameter of the neck of a narrow-mouthed resin container that contains beverages, edible oils, etc. is small (for example, 28 mm), and the corresponding injection core mold is also thin. Therefore, it was difficult to arbitrarily design the thickness of the body of the preform using the conventional method.

In contrast, in the configuration of this embodiment, the preform 20 is provided with a portion (step portion 22) that protrudes from the lower end of the neck portion 22 in the outer diameter direction, and the step portion 22 is connected to the body portion 23. This eliminates the above-mentioned restrictions caused by the injection core mold, and makes it possible to design the thickness of the body portion 23 of the preform 20 as desired. In addition to this, the body portion 23 can also be formed so that its inner wall surface gradually inclines toward the center of the preform 20 as it approaches the bottom portion 24 of the preform 20. In other words, the inner diameter of the body portion 23 can also be formed so that it gradually becomes smaller as it approaches the bottom portion 24 of the preform 20. Therefore, it is easy to design the body portion 23 of the preform 20 to be thicker. By forming the body portion 23 of the preform to be thick in this way, a high stretch ratio can be achieved during blow molding, and the physical properties (strength and rigidity) of the shoulder portion and body portion of the resin container 30 can be ensured.

As described above, according to the above-mentioned method for manufacturing a resin container, by performing post-cooling in the temperature adjustment step S2, it is possible to shorten the molding cycle time while making it difficult for defects such as residual wall to occur in the shoulder portion 36 of the resin container 30. As a result, it is possible to manufacture a resin container 30 having an appropriate wall thickness distribution by a high-cycle hot parison blow molding method.
In addition, when the heater 206 is provided, it is also possible to adjust the temperature (heat amount) of the step portion 22 by heating, so that it is possible to more precisely control the temperature of the step portion 22. This allows the preform 20 to be blow molded at a more appropriate temperature, so that it is possible to further improve the shaping property of the preform 20 in the blow molding.

According to the above-mentioned method for manufacturing a resin container, in the injection molding process S1, the step portion 22 is formed by the mold closing surfaces of the inner step defining portion 122 of the injection core mold 104, the outer step defining portion 112 of the neck mold 102, and the outer step defining portion 134 of the injection cavity mold 106. This allows a thick upper step portion 22a to be formed in the portion that is in contact with the neck mold 102 for a long time. Therefore, in the portion where heat is easily lost by the mold and is likely to cause residual material defects, a thick step portion 22 can be formed to increase the amount of heat retained.

According to the above-mentioned method for manufacturing a resin container, in the injection molding step S1, the step portion 22 and the body portion 23 of the preform 20 are molded so that their outer wall surfaces are approximately flush with each other. The inner wall surface of the body portion 23 is formed so that it gradually slopes toward the center of the preform as it approaches the bottom portion 24 of the preform 20. This allows the resin container 30 to be stretch-blow-dried well from the neck portion 21 to the shoulder portion 36, for example, even in the case of a wide-mouthed resin container 30, while optimizing the weight increase and stretching condition of the resin container 30.

Furthermore, according to the resin container manufacturing apparatus 10 having the above-mentioned configuration, the same effect as the above-mentioned manufacturing method can be obtained.

(Modification)
Fig. 7 is a diagram for explaining a support ring formed on the neck portion 21. Fig. 7F7A is a diagram showing a protrusion 25 (support ring) formed on the neck portion 21 of the preform 20 by injection molding. Fig. 7F7B is a diagram showing a protrusion 25 (support ring) formed on a resin container 30 manufactured by blow molding the preform 20 shown in Fig. 7F7A.
In the injection molding step S1, the protrusion 25 is molded on a part of the neck portion 21 of the preform 20, for example, on the lower end of the neck portion 21, as shown in F7A in Fig. 7. The protrusion 25 is molded on the lower end of the neck portion 21 and above the step portion 22. The protrusion 25 is a brim-shaped protrusion that protrudes outward from the outer periphery of the neck portion 21. The outer diameter of the protrusion 25 is molded to be larger than the outer diameter of the step portion 22.
In the blow molding process S3, the convex portion 25 is molded above the step portion 22, which is molded so that at least a portion of the step portion 22 remains between the neck portion 21 and the shoulder portion 36 in the resin container 30, as shown in F7B of Figure 7.
According to the manufacturing method for a resin container having such processes, even a resin container 30 having a support ring can be stretch-blow effectively from the neck portion 21 to the shoulder portion 36 by utilizing the heat retained in the thickness of the step portion 22.

The present disclosure is not limited to the above-described embodiments, and can be modified, improved, etc., as appropriate. In addition, the material, shape, dimensions, values, form, number, location, etc. of each component in the above-described embodiments are arbitrary and not limited as long as they can achieve the present disclosure.

For example, in this example, an example has been described in which the outer step defining portion 112 for forming a step portion is formed on the cavity surface of the neck mold 102, but this is not limited to this example. For example, as shown in Figure 8, the bottom surface of the neck mold 102 may be formed flush, and a part of the bottom surface may function as the outer step defining portion when combined with the side surface of the injection cavity mold (outer step defining portion 134) and the inner surface of the injection core mold (inner body defining portion 123).

The shape of the preform formed by injection molding is not limited to the shape described in this example. For example, as shown in FIG. 9, the thickness T3 of the body 23 of the preform 20A may be formed to be thicker than the thickness T2 of the upper end of the step portion 22. At this time, it is desirable that at least the lower step portion 22b of the step portion 22 is formed so as to gradually become thicker as it approaches the body 23. In the preform 20A of FIG. 9, it is formed so that it gradually becomes thicker from the vicinity of the boundary between the upper step portion 22a and the lower step portion 22b as it approaches the body 23, but this example is not limited to this. The starting point of the gradual thickening may be on the upper step 22a.

In addition, the thickness T2 of the upper end of the step portion 22 is preferably set between 1/3 and 9/10 of the thickness T3 of the body portion 23, and more preferably between 1/2 and 3/5. The thickness T2 of the upper end of the step portion 22 may be set, for example, between 2.0 mm and 4.0 mm.

The inner diameter of the step portion 22 is set to be the same as or smaller than the inner diameter of the neck portion 21. For example, the inner diameter of the upper step portion 22a is the same as the inner diameter of the neck portion 21, and the inner diameter of the lower step portion 22b is smaller than the inner diameter of the neck portion 21. Furthermore, in this case, it is desirable that the inner wall surface of the lower step portion 22b has a tapered shape or a curved shape with a predetermined radius of curvature.

As described above, by shaping the inner wall surface of the step portion 22 so that it approaches the central axis of the preform as it approaches the body portion 23 (by shaping the step portion 22 so that it gradually becomes thicker as it approaches the body portion), the body portion 23 of the preform 22 can be formed to be thicker. This further increases the heat retained in the body portion 23 from below the step portion 22, making it easier to ensure a high stretch ratio during blow molding. As a result, a resin container 30 can be manufactured that has an appropriate thickness distribution and ensures the physical properties (strength and rigidity) of the shoulder and body portions, as well as an aesthetic appearance.

This application incorporates as appropriate the contents disclosed in the Japanese patent application (Patent Application No. 2019-177233) filed on September 27, 2019.

Claims (7)

an injection molding step of injection molding a resin preform having a neck portion and a body portion while the neck portion is held by a neck mold ;
a temperature control step of cooling and controlling the temperature of the injection molded preform;
A blow molding process for producing a resin container by blow molding the temperature-controlled preform,
In the injection molding step,
A step portion is formed between the neck portion and the body portion of the preform, the step portion being thicker than the engagement groove of the neck portion, and the outer diameter of the step portion is formed to be larger than the outer diameter of the engagement groove of the neck portion, the step portion comprising an upper step portion that contacts the neck mold, and a lower step portion that does not contact the neck mold and has a higher retained heat than the upper step portion,
In the blow molding step,
At least a portion of the upper step portion remains as a residual step portion between a neck portion and a shoulder portion of a container blow molded based on the preform; and
The preform is blow molded at a high stretch ratio so that at least a portion of the lower step portion does not form the residual step portion in a state in which the retained heat is higher than that of the upper step portion, and a portion of the step portion forms a portion of the shoulder portion.
Manufacturing method. In the injection molding process, the step portion is formed by a mold closing surface between a neck mold and an injection cavity mold.
The method of claim 1 . In the injection molding process, the step portion and the body portion of the preform have outer wall surfaces that are substantially flush with each other, and the inner wall surface of the body portion is gradually inclined toward the center of the preform as it approaches the bottom of the preform.
The method of claim 1 . In the injection molding process, a convex portion protruding outward is formed on a part of the neck portion of the preform, and the outer diameter of the convex portion is formed to be larger than the outer diameter of the step portion.
The method of claim 1 . In the temperature control step, the body portion of the preform is cooled simultaneously from the inside and the outside.
The method of claim 1 . the remaining step portion is the step portion that contacts the neck mold, and the step portion that does not remain on the shoulder portion is the step portion that does not contact the neck mold.
The method of claim 1 . an injection molding unit that injection molds a resin preform having a neck portion and a body portion while holding the neck portion with a neck mold ;
A temperature control unit that cools and controls the temperature of the injection molded preform;
a blow molding section for blow molding the temperature-controlled preform to manufacture a resin container,
the injection molding part forms a step part between the neck part and the body part of the preform, the step part being thicker than the neck part, and the outer diameter of the step part is larger than at least the outer diameter of the engagement groove of the neck part of the preform;
The step portion includes an upper step portion that contacts the neck mold, and a lower step portion that does not contact the neck mold and has a higher retained heat than the upper step portion,
The temperature adjustment unit simultaneously cools the body portion of the preform from the inside and the outside of the body portion,
The blow molding section includes:
At least a portion of the upper step portion remains as a residual step portion between a neck portion and a shoulder portion of a container blow molded based on the preform; and
At least a portion of the lower step portion does not form the residual step portion in a state in which the retained heat is higher than that of the upper step portion , and a portion of the step portion forms a portion of the shoulder portion ,
The preform is blow molded at a high stretch ratio .
Manufacturing equipment.

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